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i386: Fix arch_query_cpu_model_expansion() leak 

Reported by Coverity:

Error: RESOURCE_LEAK (CWE-772): [#def439]
qemu-2.12.0/target/i386/cpu.c:3179: alloc_fn: Storage is returned from allocation function "qdict_new".
qemu-2.12.0/qobject/qdict.c:34:5: alloc_fn: Storage is returned from allocation function "g_malloc0".
qemu-2.12.0/qobject/qdict.c:34:5: var_assign: Assigning: "qdict" = "g_malloc0(4120UL)".
qemu-2.12.0/qobject/qdict.c:37:5: return_alloc: Returning allocated memory "qdict".
qemu-2.12.0/target/i386/cpu.c:3179: var_assign: Assigning: "props" = storage returned from "qdict_new()".
qemu-2.12.0/target/i386/cpu.c:3217: leaked_storage: Variable "props" going out of scope leaks the storage it points to.

This was introduced by commit b8097deb35 ("i386: Improve
query-cpu-model-expansion full mode").

The leak is only theoretical: if ret->model->props is set to
props, the qapi_free_CpuModelExpansionInfo() call will free props
too in case of errors.  The only way for this to not happen is if
we enter the default branch of the switch statement, which would
never happen because all CpuModelExpansionType values are being
handled.

It's still worth to change this to make the allocation logic
easier to follow and make the Coverity error go away.  To make
everything simpler, initialize ret->model and ret->model->props
earlier in the function.

While at it, remove redundant check for !prop because prop is
always initialized at the beginning of the function.

Fixes: b8097deb35
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20180816183509.8231-1-ehabkost@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Eduardo Habkost 2018-08-16 15:35:09 -03:00 committed by Paolo Bonzini
parent 5be5df720e
commit e38bf61247
1 changed files with 3 additions and 6 deletions
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9
target/i386/cpu.c
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@ -3880,6 +3880,9 @@ arch_query_cpu_model_expansion(CpuModelExpansionType type,
}
props = qdict_new();
ret->model = g_new0(CpuModelInfo, 1);
ret->model->props = QOBJECT(props);
ret->model->has_props = true;
switch (type) {
case CPU_MODEL_EXPANSION_TYPE_STATIC:
@ -3900,15 +3903,9 @@ arch_query_cpu_model_expansion(CpuModelExpansionType type,
goto out;
}
if (!props) {
props = qdict_new();
}
x86_cpu_to_dict(xc, props);
ret->model = g_new0(CpuModelInfo, 1);
ret->model->name = g_strdup(base_name);
ret->model->props = QOBJECT(props);
ret->model->has_props = true;
out:
object_unref(OBJECT(xc));